1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a shadow mask, a method of manufacturing the shadow mask and, a method of forming a thin film using the shadow mask, and more particularly, to a shadow mask including a concave-convex portion, a method of manufacturing the shadow mask, and a method of forming a thin film using the shadow mask.
2. Description of the Related Art
Recently, micro-electro mechanical system (MEMS) devices manufactured by micro-machining technology have been used in various technical applications such as display devices, laser printers, precision measurement devices, and precision processing devices. For example, a MEMS optical scanner for deflecting and reflecting scanning light is used in a display device.
Generally, the MEMS optical scanner includes a reflecting film formed on a bottom surface of a recess (a cavity) of a substrate. The width of the reflecting film is narrower than that of the cavity and a comb type driving electrode is placed at an edge of the cavity.
FIG. 1 is a cross-sectional view illustrating a related art method of forming a reflecting film of a MEMS optical scanner.
Referring to FIG. 1, a substrate SUB is prepared. A cavity (H) is formed in a surface of the substrate SUB. The bottom of the cavity (H) is flat. A shadow mask 100 is placed on the substrate SUB. The shadow mask is used for forming a thin film in the cavity (H). The shadow mask 100 includes a first opening 1 and a plurality of second openings 2, wherein the first opening 1 defines a reflecting film region in which a reflecting film will be formed, and the second openings 2 define alignment mark regions. A bottom center surface of the cavity (H) is exposed by the first opening 1. Side portions of the substrate SUB located beside the cavity (H) are exposed by the second openings 2. The shadow mask 100 is in contact with the entire surface of the substrate SUB except for the bottom surface of the cavity (H).
Then, a thin film 150 is deposited on the exposed portions of the substrate SUB by physical vapor deposition (PVD). A portion of the thin film 150 formed on the bottom center surface of the cavity (H) is a reflecting film 150a used as a mirror. The other portions of the thin film 150 formed away from the cavity (H) are used as alignment marks 150b for examining interlayer alignment states. The thin film 150 is formed by alternately depositing a Ta2O3 layer and an SiO2 layer on an Ag layer.
Though not shown, the thin film 150 is also deposited on an upper surface and a sidewall of the shadow mask 100.
After the shadow mask 100 is removed from the substrate SUB, well-known processes are sequentially performed.
In the related art method of forming the reflecting film of the MEMS optical scanner, it is difficult to control the thickness of the edge of the reflecting film 150a. The reason for this is that the gap between the bottom surface of the cavity (H) and the shadow mask 100 is very large (for example, hundreds of micrometers), and thus it is difficult to precisely define the reflecting film region in the cavity (H) of the substrate SUB using the first opening 1. When the first opening 1 cannot precisely define the reflecting film region, thin film forming particles may spread away from the reflecting film region defined by the first opening 1. Therefore, the thickness of the edge of the reflecting film 150a may vary a large amount, making it difficult to control the reflectivity of the reflecting film 150 and deteriorating the reliability of the MEMS optical scanner.